Charge set points -SW5548 vs TC60 charge controller

I've got a silly question - :blush:

Background - stacked SW5548 inverters tied to the grid - setup in Sell mode. Two 48 volt battery banks. Two TC60 charge controllers. 40 KC120-1 modules (soon to be KC120-R's - Kyocera is replacing all 40 with refurbished modules as many of the orignals have gone bad!).

I installed this in 2001 and am refreshing my memory on how everything is configured in preparation for the new module installation. Here's my question -

the SW5548 is set to float at 53 volts, bulk at 57.4 (batteries are always charged via the inverters/grid and the amps from the solar array is pushed to the grid - unless the grid is down)

the TC60's set points are 55 volts for float and 58.4 for bulk (the float is probably to high, but rarely occurs - only when the grid is down)

Is this correct to have the set points on the charge controllers be higher than the inverter charge set points (does this matter?) If this is correct, how much higher than the inverter charge volts do they need to be (I'd like to reduce from float of 55 to something closer to 53?)

Thanks,
Dave

Comments

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Charge set points -SW5548 vs TC60 charge controller

    What brand / model batteries?

    Jim / crewzer
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Charge set points -SW5548 vs TC60 charge controller

    What's your battery water usage, a little, or lots ??
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2
    System2 Posts: 6,290 admin
    Re: Charge set points -SW5548 vs TC60 charge controller

    2 battery banks of 6X8 volt Rolls 8 CS25PS batteries (12 batteries) - capacity at 20 hour rate is 820.

    Batteries are mostly on float - only used when power is out - 2 to 3 times per year. I equalize every six months and top off water - between 4 - 6 oz of water per cell (not much as each battery weighs 425 pounds - over 18" tall, 11" wide, and 28" long).

    I've changed the charge set points as follows (all charge set points are in the mfgr suggested charge rate ranges):
    SW5548 - float 53.0 and bulk 57.6
    TC60 - float 53.5 and bulk 58.6

    Thanks,
    Dave
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Charge set points -SW5548 vs TC60 charge controller

    Link to RE application charging instructions (including set points) for Rolls batteries: http://www.rollsbattery.com/files/BU-RS-614.pdf

    I have my charge controller settings right where I think they should be for my batteries, the inverter/charger is set a tad lower, and all voltmeters are normalized. My rationale is that I want the batteries to be charged from the "free" solar energy. The inverter/charger is only used to get the batteries close if they've been deeply discharged and ol' Mr. Sol is hiding.

    HTH,
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: Charge set points -SW5548 vs TC60 charge controller

    Thanks Jim. I did use these same instructions for the charge set points.

    Also, I just bought two OutBack FM60 charge controllers - upgrade to MPPT technology. Also provides easy data access via the Mate to PC for tracking energy generation. I plan to setup these new charge controllers same as my previous post:
    SW5548 - float 53.0 and bulk 57.6
    FM60 - float 53.5 and bulk 58.6

    Dave
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: Charge set points -SW5548 vs TC60 charge controller

    SW inverter will push to load (or grid depending on software rev) whenever the battery is brought higher then their set point (either in float stage or bulk stage).

    In the case for stacked units it is common for one to push to the other unit due to variation in line voltage on the L1 / L2 sides of mains and calibration tolerance between units. Another problem is the temp sensors. These temp comp voltages are step ranges of temperature about every two degrees F. When one unit hits the next step in comp voltage when the other unit is at the lower or higher level there will be a sizable push between the two units. The maximum amount of unit to unit push is dependent on maximum AC charge setting. I removed the temp sensors in my system and manually adjust the float setting when it gets cold (not often in Fla)

    You can see this effect with stacked SW's by raise the float level couple of tenths of a volt on one unit. It will start pushing DC current into the other unit. (need a DC clip-on ampmeter)

    You need to have the PV controller float level few of tenths of a volt higher then SW units.
  • System2
    System2 Posts: 6,290 admin
    Re: Charge set points -SW5548 vs TC60 charge controller

    RCinFLA,

    Sounds like my stacked SW inverters may not be very efficient (software rev is 4.10) - on the AC Input meter readout, the inverters never read the same; it does appear that one is feeding the other. Anything I can do to manage the issues you highlighted - I can remove the temp sensors, but I'm not sure that will solve any issue. What can be done about one inverter feeding the other?

    It was recommended to me to have about 1 volt difference with bulk and 0.5 for float with the inverter vs. charge controller setpoints, which I did (inverters are less than the charge controllers setpoints).

    Dave